In this paper, diode and Nd:YAG laser welding of thermoplastics will be introduced. It will be shown that laser welding of plastics can be done for parts in a lap configuration, which is the most common joint for plastics. The fact that most thermoplastics are transparent to diode or Nd:YAG laser radiation enables the laser beam to penetrate the top surface of a lap joint and reach the joint interface. Absorption in the bottom part is controlled by the type and amount of pigment used to color the plastic. By using pigments that are transparent to the laser radiation, one can therefore, weld together transparent parts to colored parts and colored parts to colored parts.
We will examine the different types of thermoplastics that can be welded and show that laser welding can provide hermetic seals. Tensile stress tests will reveal that laser welding provides welds that can be as strong as the parent material. We will also examine different types of pigments that can be used to color plastics and discuss the effect that these have on absorption of the laser beam.
Finally, applications of laser welding to the automotive industry will be discussed and some examples of parts that can be welded will be shown.